1. Field of the Invention
The present invention relates to the use of coherent energy pulses, as from high-power pulsed lasers, in the shock processing of solid materials and more particularly to a method for improving properties of solid materials by providing shock waves therein, where the laser beam impacts the solid material at spots without overlap or at varied separations. The invention is especially used for enhancing or creating desired physical properties such as hardness, strength, and fatigue strength.
2. Description of the Related Art
Known methods for the shock processing of solid materials, particularly known methods for the laser shock processing of solid materials, typically use coherent energy from a laser beam oriented normal to a workpiece.
Typical laser shock processing techniques and equipment can be found in U.S. Pat. No. 5,131,957 to Epstein.
Previous laser shock processing of workpieces include overlapping the processed areas, i.e., the laser peened spots created on the workpiece. This overlapping was accomplished to ensure that there were no gaps of worked areas on the workpiece. Furthermore, it was thought that such overlapping of processed areas (spots) would ensure that the entire worked area had a sufficient residual stress component. Different types of percentages of overlap, in terms of geometry, spacing, and such, have been utilized in the art such as 10 to 20 to 50 percent overlap of the particular processed spots on the workpiece.
A laser spot as used in this application refers to the actual workpiece surface irradiated by a laser pulse beam. A laser shocked region is that area of a workpiece in which a desired residual compressive stress field is created. Prior to this invention, large regions were laser peened with overlapping laser spots.
What is needed in the art is a time efficient process of processing such laser shock region while maintaining their requisite required residual compressive stress field.